The present invention relates to a semiconductor device and a method of manufacturing the same, and to a semiconductor device having a vertical transistor structure and a method of manufacturing the semiconductor device.
In recent years, a high-capacity and small-sized Li-ion (lithium-ion) battery has been used in various products including cell phones and notebook PCs. Although the Li-ion battery has high performance, heat generation and deterioration due to overcharge, overdischarge, short circuit or the like are likely to occur therein, and a problem such as burst arises depending on a case. A protection circuit is needed in order to safely use the Li-ion battery. Therefore, in a battery pack, there is provided a protection circuit substrate that monitors overcharge, overdischarge, overcurrent, abnormal heat generation and the like, and controls charge and discharge.
The protection circuit substrate is provided with a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a resistor, a temperature detection element and a control IC. The MOSFET switches ON/OFF a charge path and a discharge path. As the MOSFET, there is used, for example, a bidirectional MOSFET in which two FETs having a common drain electrode are formed into one chip. The resistor detects a charge and discharge current. The temperature detection element detects temperatures of the MOSFET and the protection circuit substrate, and, for example, a thermistor or the like is used as a temperature detection element. The control IC processes information from these elements, and controls the MOSFET.
With the progress of size reduction and price reduction of cell phones and notebook PCs, size reduction, thickness reduction, and price reduction are required also for the protection circuit substrate. In such a situation, a technology of mounting a temperature detection element on a MOSFET is been proposed. In Japanese Patent Laid-Open No. 2004-31980 (Patent Document 1), a temperature detection element is provided at a position adjacent to a source pad over an active region having a highest temperature over a region where a power MOSFET is formed. This temperature detection element is coupled to a control circuit formation region in a same chip, and a detection signal cannot be extracted outside.
Japanese Patent Laid-Open No. 2007-95848 (Patent Document 2) describes a technology in which two bipolar transistors coupled to gates of two output MOSFETs, respectively are provided, and in which overheated states of the output MOSFETs are detected by detecting leakage currents of the respective bipolar transistors.